CM400 are shares in a 400 MH/s mining contract.
40 000 shares for 1 Bitcent (0.01 Bitcoin) were issued, however, as at the time Bitcoin was heavily gaining in value, it was decided that additionally to the payout of the mining contract a portion of the share value will be paid out too, so the effective price per share is lower.
For more information, please consult the forum topic linked below, which is also the preferred means of communication.